Technical Abstract:
Stereotypies performed by confined sows have been implicated as indicating poor welfare. There is evidence in horses that oral stereotypies serve to buffer pH and reduce gastric ulceration. Gastric ulceration is prevalent in sows and a weak link with stereotypies has been established. The objective of this study was to determine whether stereotypic behaviors were affected by dietary NaHCO3.
Sixteen crated sows were subjected to changing diets over a 6-week period, with each animal acting as its own control. During weeks 1&2 and weeks 5&6, all sows were fed a commercial ration. During weeks 3&4, all sows were fed a commercial ration containing 2% NaHCO3. Behavior and heart rate (HR) were recorded once per week from ½h pre-feeding to 2h post-feeding. These data were analysed to determine the incidence and durations of stereotypic behaviors, posture and HR responses to feeding. Comparisons used Friedman ANOVA with dietary treatment as between-subjects factor, blocked by sow. Post-hoc comparisons used Wilcoxon signed rank tests.
Pre-feeding, sows spent 46.2% of time their engaged in stereotypies, increasing to 55.23% post-feeding (P<0.05). Pre-feeding behaviors were crate-nosing (NC=11.7%) and bar-biting (BB=11.6%). Post-feeding behaviors were floor-nosing (NF=22.3%) and sham-chewing (SC=10.2%). The post-feeding durations of BB and NF were lower after bicarbonate (BB weeks 1&2=330s, weeks 3&4=166s weeks 5&6=175s, P<0.01, NF weeks 1&2=2010s, weeks 3&4=1412s, weeks 5&6=1140s, P<0.05), but the post-feeding duration of trough-nosing (NF) increased (weeks 1&2=192s, weeks 3&4=514s, weeks 5&6=559s, P<0.001). Post-feeding, sows spent more time lying (weeks 1&2=2108s, weeks 3&4=2945s, P<0.01) and less time standing (weeks 1&2=4402s, weeks 3&4=3444s, P<0.01) when the diet contained bicarbonate. HR response to feeding was higher (p<0.01) in week 4 (163bpm) than any of the other weeks (151bpm).
Addition of dietary bicarbonate may affect both the performance of feeding-related stereotypies and the cardiac response to feeding. Further investigation is required to elucidate the mechanisms by which bicarbonate may be acting.